The present invention relates to a vinyl chloride polymer composition having excellent impact-resistance, weatherability and processability.
It hitherto has been well known that vinyl chloride polymer has excellent various properties, but has a disadvantage that impact-resistance is poor.
The so-called MBS resin obtained by graft-polymerizing methyl methacrylate, styrene, acrylonitrile, or the like, onto a butadiene rubber is widely employed as a reinforcing agent for improving an impact-resistance of vinyl chloride polymer. When MBS resin is employed as a reinforcing agent, an effect of improving the impact-resistance to vinyl chloride polymer is excellent, but double-bond of butadiene unit included in a butadiene rubber is readily deteriorated under ultraviolet light, and therefore the weatherability of vinyl chloride polymer becomes remarkably poor and it is difficult that the vinyl chloride polymer is practically employed in the outdoors.
In order to eliminate the above disadvantage that the weatherability is poor, there are proposed various methods that methyl methacrylate, styrene, acrylonitrile, or the like, is graft-polymerized onto cross-linked alkyl acrylate polymer. According to the above methods, the weatherability of vinyl chloride polymer becomes more excellent, but it is unsatisfy to improve the impact-resistance of vinyl chloride polymer. Particularly, the strength of vinyl chloride polymer cannot be increased when vinyl chloride polymer is low-kneaded with the above components. That is to say, the processability of vinyl chloride polymer is poor. The reason why the processability is poor is considered that cross-linked alkyl acrylate polymer does not have an active site for grafting, capable of graft-polymerizing onto cross-linked alkyl acrylate when the monomers are graft-polymerized onto cross-linked alkyl acrylate, unlike the case of MBS resin.
There is also proposed a method employing cross-linkable agents in which reactivities of functional groups are different. According to the above method, the impact-resistance of vinyl chloride polymer is unsatisfactorily improved.
On the other hand, there are various methods that styrene, methyl methacrylate, acrylonitrile, or the like, is graft-polymerized into a cross-linked alkyl acrylate-conjugated diolefin rubber copolymer, in which an active site for grafting is provided onto a conjugated diolefin, as in case of MBS resin. According to the above methods, the impact-resistance and processability are improved in comparison with a method employing cross-linked alkyl acrylate polymer as a rubber polymer, but the weatherability tends to become poor, because of existing conjugated diolefin in the rubber copolymer.
And also there is provided a method that the weatherability is not made poor by employing a rubber polymer, as above-mentioned. In the above method, an alkyl acrylate is copolymerized with a small amount of conjugated diolefin such that the weatherability is not made poor and the obtained copolymer is employed as a rubber copolymer. According to this method, the weatherability is improved, but the impact-resistance is unsatisfactorily improved. That is to say, as known, an effect of improving the impact resistance is increased with increasing a content of conjugated diolefin in rubber copolymer, but an effect of improving the weatherability lowers. On the other hand, an effect of improving the weatherability is increased with decreasing a content of conjugated diolefin in rubber copolymer, an effect of improving the impact-resistance lowers.
An object of the present invention is to provide a grafted copolymer having an excellent effect of improving the impact-resistance to vinyl chloride polymer by employing a small amount of a conjugated diolefin.
A further object of the invention is to provide a vinyl chloride polymer composition having an excellent impact-resistance, processability and weatherability.